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《Coastal Engineering》2005,52(2):177-195
An improved SWAN model using the Finite Element Method (FEM) was developed for wind waves simulations in both large-scale oceanic deep water regions and small-scale shallow water regions. The model employs a Taylor–Galerkin finite element technique for the discretization of the modeled area, which makes it flexible to represent bottom topography and irregular boundaries. The fractional step numerical scheme was adopted to split the wave action balance equation into three one-dimensional space equations, which can be solved efficiently by one-dimensional algorithms. The Flux-Corrected Transport method was also applied to circumvent the steep-gradients of the action density in the frequency space. The FEM code with unstructured grids improves the numerical schemes in the original SWAN to maintain computational efficiency at the operational stage. A simulation of wind wave activities for the monsoon and the 2000 Typhoon Bilis were performed using the FEM and SWAN models. The simulated results were compared with field observations in order to verify the suitability of the method. 相似文献
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Climate change, reduced sea ice and increased ice-free waters over extended areas for longer summer periods potentially lead to increased wave energy in the Beaufort Sea (Wang et al., 2015; Khon et al., 2014) [1], [2], which is a major concern for coastal and offshore engineering activities. We compare two spectral wave models SWAN (Simulating WAves Nearshore) and MIKE 21 SW (hereafter MIKE21) in simulations of storm-generated waves in the Mackenzie Delta region of the southern Beaufort Sea. SWAN model simulations are performed using two nested grids system, whereas MIKE21 uses an unstructured grid system. Forcing fields are defined by hourly hindcast winds. Moving ice edge boundaries are incorporated during storm simulations. Modelled wave spectra from four storms are shown to compare well with field observations. Two established whitecapping formulations in SWAN are investigated: one dependent on mean spectral wave steepness, and the other on local spectral steepness. For the Beaufort Sea study area, we suggest that SWAN wave simulations using the latter local spectral steepness formulation are better than those using the former mean spectral steepness formulation. MIKE21 simulations also tend to agree with SWAN results using the latter whitecapping formulation. 相似文献
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长兴岛海区波流相互作用数值模拟研究 总被引：1，自引：0，他引：1
波和流是近岸海区的主要动力因素。应用二维潮流数学模型和最新第三代近岸海浪模式SWAN,建立了非结构网格下二维情况近岸波流耦合作用数学模型。时间离散采用欧拉向前格式,空间离散采用有限体积法显式格式。通过将波浪场及潮流场进行迭代耦合计算,实现了对波流共同作用下波浪场和潮流场的数值模拟。将模型应用于矩形海湾实验和李孟国数模实验等理想地形以及大连长兴岛海区实际复杂地形算例,并用现场实测资料对计算结果进行验证,结果表明:耦合结果与实测结果吻合良好,并且要优于未耦合的结果。 相似文献
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基于加密的非结构三角网格，以Holland模型风场叠加美国国家环境预报中心（NCEP）海面风场构造的合成风场驱动第三代浅水波浪数值模型（SWAN）对2017年影响闽东海域的“纳沙”和“泰利”台风过程进行数值模拟，并运用浮标站的实测数据对模拟结果进行验证.结果表明，模型计算的风速、有效波高与实测值符合较好，合成风场能较好地模拟台风期间的风速变化过程，SWAN模式能够合理地再现闽东沿海台风浪的时空分布特征.由模拟结果可见：台风“纳沙”中心越过台湾岛进入台湾海峡北部海面，受海峡地形的约束，其波浪场呈NE—SW向椭圆状分布，北部海域的浪高大于南部，闽东沿海遍布大范围的巨浪到狂浪；超强台风“泰利”未登陆闽东，当其台风中心与大陆的距离最近时，海面波浪场分布与台风风场结构一致，台风中心附近海域为14 m以上的怒涛区，巨浪遍布于闽东沿海.研究结果可为闽东沿海台风浪灾害预警和应急管理提供技术支撑和参考依据. 相似文献
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Choi Young-Kwang Seo Seung-Nam Choi Jin-Yong Shi Fengyan Park Kwang-Soon 《海洋学报(英文版)》2019,38(7):36-47
A wave forecasting system using FUNWAVE-TVD which is based on the fully nonlinear Boussinesq equations by Chen(2006) was developed to provide an accurate wave prediction in the Port of Busan, South Korea. This system is linked to the Korea Operational Oceanographic System(KOOS) developed by Park et al.(2015). The computational domain covers a region of 9.6 km×7.0 km with a grid size of 2 m in both directions, which is sufficient to resolve short waves and dominant sea states. The total number of grid points exceeds 16 millions,making the model computational expensive. To provide real-time forecasting, an interpolation method, which is based on pre-calculated results of FUNWAVE-TVD and SWAN forecasting results at the FUNWAVE-TVD offshore boundary, was used. A total of 45 cases were pre-calculated, which took 71 days on 924 computational cores of a Linux cluster system. Wind wave generation and propagation from the deep water were computed using the SWAN in KOOS. SWAN results provided a boundary condition for the FUNWAVE-TVD forecasting system. To verify the model, wave observations were conducted at three locations inside the port in a time period of more than 7 months. A model/model comparison between FUNWAVE-TVD and SWAN was also carried out. It is found that, FUNWAVE-TVD improves the forecasting results significantly compared to SWAN which underestimates wave heights in sheltered areas due to incorrect physical mechanism of wave diffraction, as well as large wave heights caused by wave reflections inside the port. 相似文献
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《Coastal Engineering》2005,52(3):237-256
Irregular convergence behaviour is frequently encountered when computations of wave spectra are performed by means of the third-generation wind wave model SWAN (Simulating WAve Nearshore). Numerical accuracy is another key issue. The present paper proposes two techniques that improve the convergence and accuracy properties of SWAN in the prediction of stationary wave conditions in the nearshore zone. The first is an under-relaxation approach in which the extent of updates during the iteration process, which underlies a route to steady state, is made proportional to wave frequency. This method complies with the principle of decreasing time scales at higher frequencies, which is inherent to the evolution of wind waves. As a result, the improved SWAN model is free from numerical restrictions to spectral shape in the non-equilibrium range. The second proposed method is a new termination criterion associated with the rate of model convergence, by which the identification of the point of convergence is improved. The capabilities of these methods are demonstrated by simulations of idealized cases and a field application featuring fetch- and depth-limited wave growth. It is concluded that the proposed termination criterion improves numerical accuracy and that the action density limiter, as currently used in SWAN, has minimal negative influence on stationary model results. 相似文献
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Wind-wave variability in a shallow tidal sea—Spectral modelling combined with neural network methods
In this paper the wind-wave variability in the tidal basins of the German Wadden Sea is modelled with combined numerical and neural-network (NN) methods. First, the wave propagation and transformation in the study area are modelled with the state-of-the-art third-generation spectral wave model SWAN. The ability of SWAN to accurately reproduce the phenomena of interest in nonstationary conditions governed by highly variable winds, water levels and currents is shown by comparisons of the modelled and measured mean wave parameters at four stations. The principal component analysis of the SWAN results is then used to reveal the dominating spatial patterns in the data and to reduce their dimensionality, thus enabling an efficient and relatively straightforward NN modelling of mean wave parameters in the whole study area. It is shown that the data produced with the approach developed in this work have statistical properties (discrete probability distributions of the mean wave parameters etc.) very close to the properties of the data obtained with SWAN, thus proving that this approach can be used as a reliable tool for wind wave simulation in coastal areas, complementary to (often computationally demanding) spectral wave models. 相似文献
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The SWAN model used to study wave evolution in a flume 总被引：1，自引：0，他引：1
Deborah J. Wood Research Assistant Markus Muttray Research Engineer Professor Hocine Oumeraci 《Ocean Engineering》2001,28(7)
The SWAN numerical model is used to model the evolution of JONSWAP wave spectra and hence the significant wave height of waves in a tank. Comparison with experiment has shown that modelling triad interactions in the numerical model leads to too low predictions of spectra and significant wave height and should therefore be excluded. The modelling of the breaking constant was also investigated, by looking at the use of a constant breaking constant, Nelson formula, and Goda formula (added into SWAN for this study). Using a constant value of 0.78 within SWAN gave the best comparison between theory and experiment. 相似文献
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W. E. Rogers J. M. Kaihatu H. A. H. Petit N. Booij L. H. Holthuijsen 《Ocean Engineering》2002,29(11):1357-1390
The numerical schemes for the geographic propagation of random, short-crested, wind-generated waves in third-generation wave models are either unconditionally stable or only conditionally stable. Having an unconditionally stable scheme gives greater freedom in choosing the time step (for given space steps). The third-generation wave model SWAN (“Simulated WAves Nearshore”, Booij et al., 1999) has been implemented with this type of scheme. This model uses a first order, upwind, implicit numerical scheme for geographic propagation. The scheme can be employed for both stationary (typically small scale) and nonstationary (i.e. time-stepping) computations. Though robust, this first order scheme is very diffusive. This degrades the accuracy of the model in a number of situations, including most model applications at larger scales. The authors reduce the diffusiveness of the model by replacing the existing numerical scheme with two alternative higher order schemes, a scheme that is intended for stationary, small-scale computations, and a scheme that is most appropriate for nonstationary computations. Examples representative of both large-scale and small-scale applications are presented. The alternative schemes are shown to be much less diffusive than the original scheme while retaining the implicit character of the particular SWAN set-up. The additional computational burden of the stationary alternative scheme is negligible, and the expense of the nonstationary alternative scheme is comparable to those used by other third generation wave models. To further accommodate large-scale applications of SWAN, the model is reformulated in terms of spherical coordinates rather than the original Cartesian coordinates. Thus the modified model can calculate wave energy propagation accurately and efficiently at any scale varying from laboratory dimensions (spatial scale O(10 m) with resolution O(0.1 m)), to near-shore coastal dimension (spatial scale O(10 km) with resolution O(100 m)) to oceanic dimensions (spatial scale O(10 000 km) with resolution O(100 km). 相似文献
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随着海南深水网箱养殖规模的不断扩大,海浪精细化预报的需求越来越紧迫。以海南岛周边海域为目标区域,基于近岸海洋模式ADCIRC(Advancedcirculationmodel)和海浪模式SWAN(Simulating WavesNearshore),建立了海南岛近岸养殖区台风浪数值预报系统。该系统采用非结构高分辨率网格,近岸分辨率达到了100m。选取2014年第9号超强台风"威马逊"(RAMMASUN)进行针对海南岛近岸养殖区的台风浪数值模拟后报。模拟结果与实测数据较为吻合。采用全球预报系统GFS(Global Forecast System)风场和气压场数据作为驱动场对2018年7月的一次热带风暴过程进行预报,48小时、24小时预报的有效波高和实测结果比较平均相对误差分别为20.75%和17.0%。总体来说,该模型的预报精度可以满足近岸养殖区台风浪预报业务的需求。 相似文献
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《Ocean Modelling》2007,16(1-2):61-75
There is an increasing interest to move ocean codes from classical Cartesian staggered mesh schemes to unstructured staggered grids. By using unstructured grid models one may construct meshes that follow the coastlines more accurately, and it is easy to apply a finer resolution in areas of special interest.In this paper we focus on how to approximate the Coriolis terms in such unstructured staggered grid models using equivalents of the Arakawa C-grid for the linear equations governing the propagation of the inertia-gravity waves. We base the analysis on a Delaunay triangulation of the region in question and use the Voronoi points and the midpoints on the triangle edges to define a staggered grid for the sea elevation and the velocity orthogonal to the edges of the triangles. It is shown that a standard method for the Coriolis weighting may create unphysical growth of the numerical solutions. A modified Coriolis weighting that conserves the total energy is suggested.In real applications diffusion is often introduced both for physical reasons, but often also in order to stabilise the numerical experiments. The growing modes associated with the unstructured staggered grids and equal weighting may force us to enhance the diffusion more than we would like from physical considerations. The modified weighting offers a simple solution to this problem. 相似文献
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Wave-tide-surge coupled simulation for typhoon Maemi 总被引：1，自引：0，他引：1
The main task of this study focuses on studying the effect of wave-current interaction on currents, storm surge and wind wave as well as effects of current induced wave refraction and current on waves by using numerical models which consider the bottom boundary layer and sea surface roughness parameter for shallow and smooth bed area around Korean Peninsula. The coupled system (unstructured-mesh SWAN wave and ADCIRC) run on the same unstructured mesh. This identical and homogeneous mesh allows the physics of wave-circulation interactions to be correctly resolved in both models. The unstructured mesh can be applied to a large domain allowing all energy from deep to shallow waters to be seamlessly followed. There is no nesting or overlapping of structured wave meshes, and no interpolation is required. In response to typhoon Maemi (2003), all model components were validated independently, and shown to provide a faithful representation of the system’s response to this storm. The waves and storm surge were allowed to develop on the continental shelf and interact with the complex nearshore environment. The resulting modeling system can be used extensively for prediction of the typhoon surge. The result show that it is important to incorporate the wave-current interaction effect into coastal area in the wave-tide-surge coupled model. At the same time, it should consider effects of depth-induced wave breaking, wind field, currents and sea surface elevation in prediction of waves. Specially, we found that: (1) wave radiation stress enhanced the current and surge elevation otherwise wave enhanced nonlinear bottom boundary layer decreased that, (2) wind wave was significantly controlled by sea surface roughness thus we cautiously took the experimental expression. The resulting modeling system can be used for hindcasting (prediction) the wave-tide-surge coupled environments at complex coastline, shallow water and fine sediment area like areas around Korean Peninsula. 相似文献
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This study examines the effects of tides on surges, wave setups and waves, in terms of tidal amplitudes and phases, by using a coupled numerical model of Surge, WAve and Tide (called as SuWAT). The SuWAT model, composed of depth integrated nonlinear shallow water equations and Simulating WAves Nearshore (SWAN) model, is able to simultaneously run with an arbitrary number of nested domains by using the Message Passing Interface. The results for an idealized case indicate that surge and wave setup are increased in the phase of low water and decreased in the high water phase; on the other hand, waves change in a reverse manner. Such changes are enhanced by large tidal variations. The conventional method (e.g., surge plus tide independently) has the possibility of overestimation for the total water level. The hindcast results for Typhoon Ewiniar in 2006 show that the run with tides is more accurate 10% than that without tides in coastal areas of Korea. The nested scheme improves the accuracy up to 40% for the prediction of water levels in the simulations. It is shown that the present coupled model, SuWAT, is capable of predicting both water levels and waves under storm events with reasonable accuracy against the observations. 相似文献
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In order to investigate surf zone hydrodynamics through two-dimensional numerical simulations of nearshore circulation under random wave environment, a nearshore circulation model, SHORECIRC, and a random wave model, SWAN, were combined and utilized. Using this combined model, a numerical simulation of the October 2, 1997 SandyDuck field experiment was performed. For this simulation, field topography and an input offshore spectrum were constructed using observed data sets synchronized with the experiment. The wave-breaking model in SWAN was modified by using breaker parameters varied according to bottom slope. The simulation results were compared with the experimental data, which revealed a well-developed longshore current, as well as with results using other combinations which were SHORECIRC and its original monochromatic wave-driver, and SHORECIRC and the default of SWAN. The results from the novel combined model agreed well with the experimental data. The results of the present simulation also indicate that alongshore field topography influences shear fluctuation of longshore currents. 相似文献
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文章基于Delaunay三角化的思想实现了非结构化数值网格生成技术,并LOP(Local Optimization Procedure)算法对网格进行了优化。用有限体积法在非结构三角形网格上对平面二维潮流方程进行了数值求解。实例应用分析表明,文中的数值网格生成技术和有限体积方法相结合用于求解具有复杂几何边界区域内的潮流问题能取得很好的结果。 相似文献